The chemistry, including radiochemical synthesis, the metabolism and biological role will be studied of furan fatty acids which recently have been discovered in the liver and testes of northern pike and some other fish. Their structure consists of a furan ring substituted by one or two methyl groups and by two aliphatic straight chains which have a terminal methyl and a carboxyl group, respectively. Methods for chemical synthesis of these and closely related furan fatty acids will be worked out. Major emphasis will then be given to radioactive syntheses, including possible biological precursors and degradation products. These compounds will serve to locate the tissues which synthesize the furan acids and to map the sequence of metabolites. Eventually, we hope to characterize subcellular fractions and enzymes involved in these processes. Fish from natural habitat, from rearing stations and from laboratory colonies will be used in these studies. The furan fatty acids have been found at relatively high levels in northern pike, blue gill, rock bass, brook trout and bullhead. They occur at much lower level in gourami of which we have an established colony. In all cases, the investigations will be facilitated by the fact that the furan fatty acids are greatly enriched in cholesteryl esters. The species to be used for detailed metabolic experiments will be under dietary control.